Conventionally, as shown in FIGS. 5A and 5B, stroboscopic device 13 proposes to change an irradiation angle of a light ray by varying a distance between light controller member 18 and light source 15 in order to correspond to a change in shooting range (lens zooming). This stroboscopic device includes light emitter 17 disposed in light-emitter casing 14 and light controller member 18 disposed in an opening of light-emitter casing 14 for controlling the light ray from light emitter 17. Light emitter 17 includes light source 15 and reflector 16 that reflects the light rays (light flux) from light source 15 in an irradiation direction (left hand when looking at the drawing from the surface).
FIGS. 5A and 5B are vertical sectional view of light-emitter casing 14 of stroboscopic device 13. FIG. 5A shows the position of light-emitter 17 at a telephoto end. A flash coverage of stroboscopic device 13 in this position is indicated by the chain line. FIG. 5B shows the position of light-emitter 17 at a wide-angle end. A flash coverage of stroboscopic device 13 is indicated by the chain line.
This type of stroboscopic device 13 may have a broadened irradiation angle to meet the use of ultra-wide lens. However, there are the light rays (see the chain line in FIG. 5A) that do not enter light controller member 18 provided in the opening of light-emitter casing 14 when light controller member 18 is at a point distant from light source 15. This results in a loss of light.
To prevent such loss of light, a conventional stroboscopic device (illumination optics) disclosed in PTL 1 includes a light source (xenon tube), a reflective member (reflector) reflecting the light ray from the light source toward the light controller member (Fresnel lens), and a reflective plate extending between an end of the reflective member at the telephoto end and an end of light controller member, whose inner circumferential face is a reflective face. The stroboscopic device configured in this way reflects the light rays that do not enter the light controller member at the reflective face of the reflective plate to make the light ray enter the light controller member. (For example, see paragraph [0020] to [0026] of PTL 1.)
A conventional stroboscopic device (lighting device with variable irradiation angle) disclosed in PTL 2 includes a light source (flash discharge tube), a reflective member (reflector) for reflecting the light rays from the light source to a light controller member, a first translucent optical member that divides the light rays from the light source into multiple light paths, and a second translucent optical member with multiple cylindrical lens faces for converting the light rays from the first translucent optical member to an intended light distribution characteristic. The stroboscopic device as configured above controls the light rays from the light source by changing a distance between an outgoing face of the first translucent optical member and the incoming face of the second translucent optical member. The light rays are refracted at an intended irradiation angle at each of multiple cylindrical lens faces of the second translucent optical member, and enters the light controller member (for example, see paragraph [0024] to of PTL2).
However, in the conventional stroboscopic device disclosed in PTL1, uneven irradiation may occur if the light reflects at a joint of the reflective member and the reflective plate at an unexpected angle. In addition, a movable mechanism of the reflective member makes the structure complicated.
In the conventional stroboscopic device disclosed in PTL2, the irradiation angle is broadened by crossing the light rays from the light source by means of the light-collecting effect of the first translucent optical member and the light-collecting effect of the second translucent optical member. However, to satisfy a demand for further wider irradiation angle, the refractive power of the first and second translucent optical members need to be further increased.
More specifically, the conventional stroboscopic device disclosed in PTL2 refracts the light rays by curvature of the outgoing face of the second translucent optical member so as to mutually cross the light rays to widen the irradiation angle.
However, if the refractive power of the second translucent optical member is increased to achieve further wider irradiation angle, the light rays cross at the telephoto end, due to excessive refractive power of the second translucent optical member. This risks inability to collect light at an optimal irradiation angle at the telephoto end.